contextmenu / draggable

[fred-wang]

Originally reported at https://gitlab.com/mathml/MathMLinHTML5/issues/7

Created by: Yaffle
Any chance to have support for these attributes for MathML elements on web page?

Created by: fred-wang
Note that http://www.mathml-association.org/MathMLinHTML5/ is an implementation note for a core subset of MathML in HTML5, not a standard specification. If these attributes are allowed by the HTML5 & MathML W3C specifications and if there is a strong use case for them, then they could be added. But probably that would be in later versions since we want to implement the core subset in web engines first.

Created by: Yaffle
tabIndex, focus and blur were added to SVG elements, not good that this addition occurred not on the Element interface.
A hack can be used to make an element focusable+draggable in Firefox - <mrow href="#">, but this is still a hack and no way to call element.focus().

[fred-wang]

See also #129 for the general issue.

[fred-wang]

draggable: https://html.spec.whatwg.org/multipage/dom.html#elements-in-the-dom:dom-draggable
tabindex: https://html.spec.whatwg.org/#elements-in-the-dom:dom-tabindex

I'm not sure whether the reported meant
oncontextmenu: https://html.spec.whatwg.org/multipage/webappapis.html#idl-definitions:handler-oncontextmenu
or
contexmenu: https://www.w3.org/TR/html51/interactive-elements.html#element-attrdef-global-contextmenu

[fred-wang]

tabindex is now supported, so changing title

[Yaffle]

In Chrome it is possible to make a MathML element draggable using:

[draggable="true"] {
  -webkit-user-drag: element;
  user-select: none;
}

Of course, it should not be used, as -webkit-user-drag is a non-standard property.

[NSoiffer]

Unless I'm missing something, it doesn't make sense for a MathML element to be dragable in general because some elements need to live in certain contexts (e.g, a table row needs to live in a table and all elements need to live inside of a math element. Other cases can be problems too. E.g, dragging a numerator elsewhere leaves a fraction element with too few children, and the repair mechanism would cause the denominator to become the numerator, which is probably not intended.

It would be possible to describe situations where drag and drop is legal/sensible, but I don't think the effort is worth the benefit. Editing a MathML expression is best left to MathML editors IMHO.

[Yaffle]

@NSoiffer , the draggable attribute does not do the removal of the element by itself, the JavaScript should handle dragstart event.

[fred-wang]

I'm not sure whether the reported meant
oncontextmenu: https://html.spec.whatwg.org/multipage/webappapis.html#idl-definitions:handler-oncontextmenu
or
contexmenu: https://www.w3.org/TR/html51/interactive-elements.html#element-attrdef-global-contextmenu

@Yaffle Can you please clarify?

[fred-wang]

cc @bkardell

[Yaffle]

Both of them,
An example can be found at https://developer.mozilla.org/en-US/docs/Web/HTML/Global_attributes/contextmenu .

Well, right not, it is only supported in Firefox and not sure if it is useful (may be, I could collect info how many users use it). So, the support is not so much important right now. And it was deprecated in HTML spec, where it was defined on all elements....
Firefox supports "contextmenu" attribute on MathML elements, but does not fire "oncontextmenu" event (which is useful when you need to adjust or "setup" the menu for the specific element if you are sharing the same <menu> element..., but the event is easy to polyfill (just listen on the document))